The move boosts Bradley at a time when he is gaining in polls, and fuels speculation that the New Jersey Democrat can carry New York, whose 2000 primary comes on March 7, early enough to sway other states.

The endorsement deals another setback to Vice President Al Gore, whose campaign is sagging in New York and nationally. Some polls suggest Bradley would be a stronger Democratic nominee against GOP front-runner George W. Bush.

“They’ve known each other for a quarter-century and Moynihan thinks the world of Bradley and is ready to campaign hard to help him,” said a source close to New York’s senior senator.

Moynihan’s embrace of Bradley and readiness to stump hard for him also poses a quandary for Hillary Rodham Clinton, who is seeking Moynihan’s Senate seat but has vowed to back Gore.

That means Mrs. Clinton will find herself early next year campaigning on the opposite of the New York political icon she’s trying to replace and whom she has painted as her political mentor.

Sources said Moynihan’s wife, Liz, always his closest political adviser and the mastermind of his campaigns, was actively involved in his decision to endorse Bradley.

One source close to Moynihan said the retiring senator feels Bradley – before he himself left Congress – was one of the shrinking number of senators who lived up to Moynihan’s ideal.

Moynihan “remembers that when he first came to the Senate, it was filled with real giants and he doesn’t think there are many like that now,” the source said.

Moynihan aides have long indicated that he would back Bradley when he thought it would do the most good. The timing was up to the ex-Knick, who was eager for an endorsement now to fuel a growing sense of momentum.

Polls show Bradley in a statistical tie with Gore in New York, in New Hampshire, which holds the nation’s first primary, and in Massachusetts.

Moynihan is Bradley’s third Senate endorsement – following liberal Paul Wellstone (D-Minn.) and centrist Bob Kerrey (D-Neb.), a close friend – and it could ease the way for other senators to break with the White House.

Moynihan’s endorsement also could make it easier for other New Yorkers to buck the establishment and go with Bradley, as a few dozen Brooklyn Democrats did last week.

The Gore campaign, apparently hoping to counter the blow from the Moynihan endorsement, released a list of nine New York endorsements for Gore, several of whom were already known. The list included Reps. Charles Rangel (D-Manhattan) and Nydia Velazquez (D-Brooklyn).